This invention relates to a numerical control system, and more particularly, to a numerical control system that permits the execution of a variety of special processes suited to the user's needs without requiring modifications in the software for the numerical control device.
A numerical control device is adapted to execute numerical control processing on the basis of a command program acquired from a paper tape or the like, a machine tool being actuated in accordance with the processing results so as to machine a workpiece in the manner specified by the program.
The conventional command program is composed of move commands, speed commands, miscellaneous function instructions that constrain a machine tool to perform prescribed operations, S-function instructions instructive of spindle speed, T-function instructions that command a tool change, preparatory function instructions and the like. Instructions for the execution of prescribed processes based on the status of the machine tool or numerical control device (hereinafter called NC) cannot be inserted into the command program with the conventional systems. Until now this inability to perform such processing has not caused any major inconvenience in the execution of ordinary numerical control but, as the demand for NC's of improved performance grows, so will the requirement for functions that allow processing in accordance with machine tool and NC conditions to be achieved by means of a command from the command program.
A numerical control device is a computer that includes a central processing unit (CPU), a control program memory and a data memory, and is adapted to control a machine tool on the basis of both a control program and a command program which the CPU obeys in executing the predetermined numerical control processing. The software for the computer numerical control device (hereinafter called CNC) of this type is created so as to make possible standardized control of machine tools. There are occasions, however, where specialized machine tool control is required for certain machines or in order to meet certain customer requirements even when identical machines are employed. In such instances it is conventional practice to modify the CNC software for the particular case to enable the execution of control in accordance with the specific specifications. In other words, it has been necessary for the NC manufacturer to modify the NC software in order to satisfy the particular machine tool control requirements. This has necessitated an exorbitant amount of time and labor and an increase in labor costs.